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PubMed1980

Chemical characterization and substrate specificity of rabbit liver aryl sulfatase A.

Rabbit liver aryl sulfatase A (aryl-sulfate sulfohydrolase, EC 3.1.6.1) is a glycoprotein containing 4.6% carbohydrate in the form of 25 residues of mannose, seven residues of N-acetylglucosamine, and three residues of sialic acid per enzyme monomer of molecular weight 140 000. Each monomer consists of two equivalent polypeptide chains. The protein has a relatively high content of proline, glycine and leucine, and the amino acid composition of rabbit liver aryl sulfatase A is similar to that of other known liver sulfatases. Rabbit liver aryl sulfatase A catalyzes the hydrolysis of a wide variety of sulfate esters, although it appears possible that cerebroside sulfate is a physiological substrate for the enzyme because the Km is very low (0.06 mM). The turnover rate for hydrolysis of nitrocatechol sulfate or related synthetic substrates is much higher than the rate with most naturally occurring sulfate esters such as cereroside sulfate, steroid sulfates, L-tyrosine sulfate or glucose 6-sulfate. However, the turnover rate with ascorbate 2-sulfate is comparable to the rates measured using most synthetic substrates. These results are discussed in relationship to several previously described sulfatase enzymes which were claimed to have unique specificities.

Amino Acids↗
PubMed1983

Human placental steroid sulfatase: purification and properties.

Steroid sulfatase is recovered quantitatively from the 105,000 g h supernatant of human placental microsomes extracted with Triton X-100. The solubilized enzyme has been purified using conventional techniques. Throughout the purification procedure, steroid sulfatase appears to be heterogeneous as evidenced by certain, but not all, criteria. Following polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the final preparation exhibits a major component and varying amounts of two minor ones. Antibodies raised in rabbits with the heterogeneous immunogen give rise to a single precipitation line when the native enzyme is analyzed by double immunodiffusion or by immunoelectrophoresis. In addition, using aged preparations of microsomes and immunoaffinity techniques, steroid sulfatase activity was found to be associated with the fastest migrating minor component. This finding would suggest that the apparent heterogeneity of purified steroid sulfatase is linked to degradation processes occurring within the microsomal preparations. Steroid sulfatase has a Stokes radius of 56 A, a sedimentation coefficient of 4.85 +/- 0.15S (in Triton-containing buffers) and binds 1.3 g of Triton X-100-per g of protein. The molecular weight of the Triton-protein complex was calculated to be 166,000 in which the glycoprotein portion contribution is about 43% (72,000). In contrast, the apparent molecular weight of the major polypeptide determined on calibrated SDS-gels is 62,000. The purified enzyme exhibits two pH optima with cholesterol sulfate as substrate, an acidic one at pH 5.0 and a second one at pH 7.5. The Km values for cholesterol sulfate, dehydroandrosterone sulfate and p-nitrophenylsulfate were 5.26, 14 and 1,320 microM, respectively.

Detergents↗
PubMed1984

Steroid sulfatase activities in normal and cirrhotic livers and plasma levels of estrone sulfate, estrone and estradiol-17 beta in men.

Estrone and dehydroepiandrosterone (DHEA) sulfatases were studied in livers of normal and cirrhotic men. Their Km were 3.2 microM and 1.2 microM respectively. The microsomal sulfatases were solubilized by Miranol H2M and ultrasound. After gel filtration, the soluble material gave a single peak of activity for both substrates with a molecular weight of approximately 330,000. In terms of pmol of product.min-1 per mg of fresh tissue, the mean (+/- SD) values of estrone and DHEA sulfatase activities were lower in cirrhotic livers [(n = 7) (4.09 +/- 2.90 and 0.38 +/- 0.20)] than in normal livers [(n = 13)(8.29 +/- 4.00 and 0.69 +/- 0.20)]. The differences were statistically significant : p less than 0.03 for estrone sulfatase and p less than 0.01 for DHEA sulfatase. In cirrhotic men, the mean level of plasma estrone is increased whereas that of estrone sulfate is decreased. The variations may be related to the decrease of serum albumin in cirrhotic subjects.

Adult↗
PubMedDate not supplied

Lack of correlation between steroid sulfatase activities and lipid content in uterus and liver microsomes of guinea pigs.

Lipid content and steroid sulfatase activities were determined in liver and uterus microsomes of non-pregnant guinea pigs. The results were compared with values obtained in pregnant and cortisol-treated animals. Steroid sulfatase activities were always higher in pregnant animals, and we supposed that the increase in circulating cortisol in pregnant guinea pigs before parturition has an influence on the membrane-bound sulfatase activities. Sulfatase activities were identical in cortisol-treated and untreated non-pregnant females, although cortisol induced changes in microsomal lipid composition. These results lead us to three conclusions: in intact female guinea pigs, cortisol induces variations in the lipid content of uterus and liver microsomes, especially in the cholesteryl sulfate to phospholipid ratios; the variations of the lipid composition in pregnant animals do not appear to be cortisol-dependent; membrane-bound steroid sulfatase activities are not directly influenced by the lipid composition of microsomes.

Animals↗
PubMed2003

In vitro and in vivo models for the evaluation of new inhibitors of human steroid sulfatase, devoid of residual estrogenic activity.

The goal of our research project is to develop a new class of orally active drugs, estrone sulfatase inhibitors, for the treatment of estrogen-dependent (receptor positive) breast cancer. Several compounds were synthesized and their pharmacological potencies explored. Based on encouraging preliminary results, three of them, TX 1299, TX 1492 and TX 1506 were further studied in vitro as well as in vivo. They proved to be strong inhibitors of estrone sulfatase when measured on the whole human JEG-3 choriocarcinoma and MCF-7 breast cancer cells and their IC(50)s found to be in the range of known standard inhibitors. Their residual estrogenic activity was checked as negative in the test of induction of alkaline phosphatase (APase) activity in whole human endometrial adenocarcinoma Ishikawa cells. In addition, their effect on aromatase activity in JEG-3 cells was also examined, since the goal of inhibiting both sulfatase and aromatase activities appears very attractive. However, it has been unsuccessful so far. Then, in vivo potencies of TX 1299, the lead compound in our chemical series, were evaluated in comparison with 6,6,7-COUMATE, a non-steroidal standard, in two different rat models and by oral route. First, the absence of any residual estrogenic activity for these compounds was checked in the uterotrophic model in prepubescent female rats. Second, antiuterotrophic activity in adult ovariectomized rat supplemented with estrone sulfate (E(1)S), showed that both compounds were potent inhibitors, the power of TX 1299 relative to 6,6,7-COUMATE being around 80%. This assay was combined with uterine sulfatase level determination and confirmed the complete inhibition of this enzyme within the target organ. Preliminary studies indicated that other non-steroid compounds in the Théramex series were potent in vitro and in vivo inhibitors of estrone sulfatase in rats and further studies are in progress.

Animals↗
PubMed2002

Sulfamoyloxy-substituted 2-phenylindoles: antiestrogen-based inhibitors of the steroid sulfatase in human breast cancer cells.

Estrone sulfate (E1S) is an endogenous prodrug that delivers estrone and, subsequently, estradiol to the target cells following the hydrolysis by the enzyme estrone sulfatase which is active in various tissues including hormone dependent breast cancer cells. Blockade of this enzyme should reduce the estrogen level in breast cancer cells and prevent hormonal growth stimulation. Sulfamates of a variety of phenolic compounds have been shown to be inhibitors of estrone sulfatase. Our rational is based on findings that these inhibitors can undergo hydrolysis and the pharmacological effects of the free hydroxy compounds contribute to the bioactivity of the sulfamates. A desirable action of the metabolites would be an estrogen antagonism to block stimulatory effects of residual amounts of estrogens. Thus, we synthesized a number of sulfamoyloxy-substituted 2-phenylindoles with side chains at the indole nitrogen that guarantee antiestrogenic activity. All of the new sulfamates were studied for their inhibitory effects on the enzyme estrone sulfatase from human breast cancer cells and their (anti)hormonal activities in stably transfected human MCF-7/2a mammary carcinoma cells. The hormonal profile of the sulfamates was partly reflected by the properties of the corresponding hydroxy precursors. Some of the sulfamoylated antiestrogens strongly inhibited estrone sulfatase activity with IC(50) values in the submicromolar range. They were devoid of agonist activity and suppressed estrone sulfate-stimulated gene expression mainly by blocking the enzyme. Examples are the disulfamates of the indoles ZK 119, 010 and ZK 164, 015. Their IC(50)s for sulfatase inhibition were 0.3 and 0.2 microM, respectively, and 50 and 80 nM, respectively, for the inhibition of E1S-stimulated luciferase expression in transfected MCF-7 cells. With some of the new sulfamates an additional direct antiestrogenic effect was noticed which might be due to a partial hydrolysis during incubation and would improve the growth inhibitory effect on estrogen-sensitive breast cancer cells.

Arylsulfatases↗
PubMed1980

Complementation of arylsulfatase A in somatic hybrids of metachromatic leukodystrophy and multiple sulfatase deficiency disorder fibroblasts.

Metachromatic leukodystrophy and multiple sulfatase deficiency disorder are severe neurodegenerative diseases inherited as separate autosomal recessive traits. Arylsulfatase A (aryl-sulfate sulfohydrolase, EC 3.1.6.1) activity is deficient in both diseases but in multiple sulfatase deficiency disorder, activities of arylsulfatases B and C and other sulfatases are also reported to be reduced. Somatic hybrid cell clones produced by fusing cultured fibroblasts from patients with these diseases were isolated by a nonselective technique based on unit-gravity sedimentation. Arylsulfatase A activity was restored in these hybrids. The complemented enzyme resembled the normal arylsulfatase A in heat stability, pH optimum, Km, electrophoretic mobility, and immunologic reactivity. Because a structurally normal enzyme can be restored in a hybrid only though intergenic complementation, these results indicate that the mutations responsible for the deficiency of arylsulfatase A activity in metachromatic leukodystrophy and multiple sulfatase deficiency disorder are nonallelic and that at least two genetic loci control the expression of arylsulfatase A activity in the human genome. Furthermore, arylsulfatase C activity was also restored to normal in the hybrids, indicating that a common sulfatase inhibitor is not the cause of the multiple sulfatse deficiency.

Cells, Cultured↗
PubMed1987

Cloning of a cDNA for steroid sulfatase: frequent occurrence of gene deletions in patients with recessive X chromosome-linked ichthyosis.

A human steroid sulfatase (steryl-sulfatase; steryl-sulfate sulfohydrolase, EC 3.1.6.2) cDNA 2.4 kilobases long was isolated from a human placental lambda gt11 cDNA expression library. The library was screened with monospecific rabbit antibodies elicited by injection of steroid sulfatase protein purified from human placentas. Hybridization of the cDNA with EcoRI-digested genomic DNA indicated that patients from 14 of 15 apparently unrelated families have gross deletions of the gene for steroid sulfatase. One patient had genomic DNA fragments that were identical to those from normal individuals, indicating the absence of any major deletions as the cause of his lack of steroid sulfatase enzyme activity.

Chromosome Deletion↗
PubMed1985

Steroid sulfotransferases and steroid sulfate sulfatases: characteristics and biological roles.

This review discusses the biological roles of steroid sulfotransferase enzymes (ST's) and steroid sulfate sulfohydrolases (sulfatases) mainly in mammalian tissues. In addition, some consideration is given to certain characteristics of these enzymes and, where possible, to their biological control. A considerable number of ST's of varying specificities, substrate affinities, and kinetics appear to exist. Several of these possess the properties of regulatory enzymes. ST's which act upon estrogen in reproductive tissues, such as uterus, are of particularly high affinity, appear to be under some biological control, and may exert important effects upon estrogen action. Although biosynthetic pathways involving steroid sulfate intermediates have been described, their importance is difficult to determine. The presence of an esterified sulfate group on a steroid molecule may markedly affect the action of enzymes, such as hydroxylases, upon the steroid structure in both a qualitative and quantitative sense. The number of different steroid sulfatases is not well understood. A sterol sulfatase present in the female reproductive tract appears capable of destabilizing the sperm head membrane by hydrolyzing sterol sulfates necessary for its integrity, and hence enabling the fusion of sperm and ovum. Other sulfatases may utilize blood-borne steroid sulfates for the ultimate production of estrogen which, in fetal membranes, could play a role in parturition and, in breast tumours, could function as a growth promoting agent. Brain sulfatases could possibly produce steroid hormones for purposes of tissue differentiation and (or) feedback control mechanisms, but this is not firmly established.

Adrenal Cortex↗
PubMed1976

Iduronate sulfatase activity in serum, lymphocytes, and fibroblasts--simplified diagnosis of the Hunter syndrome.

A previously described assay for iduronate sulfatase has been adapted for use with serum, lymphocytes, and fibroblasts. The assay also gives a rough measure of iduronidase activity. We have evaluated the procedure for the diagnosis of the Hunter syndrome, for the detection of Hunter heterozygotes, and for the diagnosis of certain other disorders (mucolipidoses II and III and mucopolysaccharidosis I). Hunter patients had 1-2% normal iduronate sulfatase activity in the three sources tested. The serum assay is undoubtedly the method of choice to establish the diagnosis of the Hunter syndrome. Less that 1 ml serum and 3-4 days are required to complete the procedure. Serum could not be used for the detection of iduronidase deficiency diseases, but these could easily be recognized in lymphocyte and fibroblast preparations. The iduronate sulfatase activity of sera from patients with mucolipidoses II and III was elevated 20-fold, but their parents had a normal level of the enzyme. In fibroblasts of patients with mucolipidoses II and III, both iduronate sulfatase and iduronidase activities were markedly decreased. Serum assays were not informative about the Hunter heterozygote status. However, the mean activity in lymphocytes from mothers of Hunter patients was about half of the mean normal activity. A number of obligate heterozygotes had iduronate sulfatase activity so low that they were identifiable as carriers; others, unfortunately, had a clearly normal level. The possibility of carrier detection by the lymphocyte assay needs further development.

Female↗
PubMed1990

Estrone sulfate sulfatase activity is increased during in vitro decidualization of stromal cells from human endometrium.

Arylsulfatase (EC 3.1.6.1) activity in human stromal cells isolated from specimens of histologically normal proliferative endometrium was increased several-fold during culture for 8-15 days in RPMI-1640 medium plus 10% charcoal-treated fetal bovine serum in the presence of a mixture of ovarian hormones (36 nM estradiol, 1 microM medroxyprogesterone acetate, and 100 micrograms/mL relaxin). The changes in sulfatase activity, determined by measuring the rate of formation of estrone from tritiated estrone sulfate, were associated with in vitro decidualization of the stromal cells, as determined by changes in secretion of PRL into daily renewed culture medium. PRL output by the cells during the last 24 h in culture and sulfatase activity in the cells collected at the end of the culture period were related to their DNA and protein contents. Sulfatase activity in the cells cultured in the presence of the ovarian hormones was comparable to the activity found in decidual cells at term pregnancy. PRL added for 1 day to cultures of stromal cells in the absence of exogenous hormones increased sulfatase activity in the cells, probably by acting in an autocrine manner, as previously demonstrated with human decidual cells during pregnancy. These experiments also revealed a hormonal regulation of stromal cell proliferation in vitro, as estimated from measurements of both DNA and protein levels per dish. Augmentation of sulfatase activity can serve as another marker of in vitro decidualization. Physiologically, an increase in this enzymatic activity may result in a preferential estrogenic stimulation of the decidualized cells by utilization of a circulating substrate, estrone sulfate. This hypothesis could explain the preferential retention of progesterone receptors in decidual cells observed immunohistochemically during the late luteal phase of the menstrual cycle, suggestive of a shift in progestogenic actions from the epithelium to the stroma.

Arylsulfatases↗
PubMed1987

[Steroid sulfatase and placental deficiency. Current data as instigators of new research].

Arylsulfate sulfohydrolases, ubiquitously distributed, mediate the hydrolysis of sulfoconjugated steroids found in large amounts in a variety of human tissues and fluids. The sterol sulfate sulfohydrolase (steroid sulfatase), bound to the microsomal fraction, is capable of hydrolyzing natural substrates such as cholesterol and dehydroepiandrosterone sulfates. The placenta is the richest source of the enzyme. The physiological interest of this enzymatic activity became apparent when placental steroid sulfatase deficiency was described in pregnancies with strikingly low oestrogen levels in the maternal plasma and urine. This enzymopathy appears to have only a moderate pejorative incidence on the mode of delivery, thus intervention is unnecessary unless dictated by fetal and/or maternal associated pathology. The disorder is transmitted on the X-linked recessive mode of inheritance and affected individuals, all males, present with ichthyoses of the sex-linked type. The gene coding for the steroid sulfatase enzyme has been assigned to the distal part of the X-chromosome in the Xp22.3-Xpter region which is known to escape the inactivation process. The lack of enzymatic activity in the somatic tissues of the patients is followed by an increase of the circulating sulfated steroid levels and by an accumulation of cholesterol sulfate in blood and skin. The modified electrophoretic mobility of the low-density lipoproteins, which might result from the excess of cholesterol sulfate bound to these lipoproteins, is a new diagnostic clue for the enzymopathy. Apart from the modification recognized to be systematically associated to the steroid sulfatase deficiency, numerous cases of hypogonadism and cryptorchidism have been recently described and may be considered as new clinical manifestations of this genetic disorder. Recent cloning of the gene coding for the steroid sulfatase should allow the molecular study of the etiology of this inborn error of metabolism.

Female↗
PubMed1982

[Microsomal sulfatase deficiency in X chromosome-linked ichthyosis].

The microsomal sulfatases are known to be deficient in the X-linked recessive inherited type of ichthyosis (XLI), which is closely related to the placental steroid-sulfatase deficiency. Our group demonstrated biochemically the deficiency of steroid-sulfatase activity as well as arylsulfatase C activity in cultured skin fibroblasts and leukocytes of patients with XLI, whereas all cases of ADI investigated hitherto expressed high activities of microsomal sulfatase. On the other hand, the analysis of microsomal sulfatase in membranous preparations of uncultivated skin and hair follicles failed to distinguish between XLI, ADI, and controls. Possible relations between this enzyme defect and the hyperkeratotic condition of XLI are discussed.

Arylsulfatases↗
PubMed1997

Concentrations of estrone, estradiol and their sulfates, and evaluation of sulfatase and aromatase activities in patients with breast fibroadenoma.

In the present studies, the concentrations (mammary tissue and plasma) of estrone (E1), estradiol (E2) and their sulfates (E1S and E2S), as well as the sulfatase and aromatase activities, were evaluated in patients with breast fibroadenomas. Comparative studies of the evaluation of these parameters were carried out in: (A) tumor tissue, (B) areas surrounding the tumor and (C) areas distant from the tumor (glandular tissue) considered as normal tissue. The concentrations in the tumor tissue (in pmol/g tissue) of E1, E2 and E1S were significantly higher (2-3 times) than in the area of the breast considered as normal. Sulfatase and aromatase activities were found in the breast fibroadenoma tissue. Sulfatase activity was much higher than aromatase (30-150 times) and sulfatase levels were significantly higher in the fibroadenoma tissue than in the area considered as normal. Plasma evaluation of E1, E2, E1S and E2S concentrations showed no significant differences in relation to those of healthy control women. In conclusion, the high levels of estrogens and their sulfates, as well as the enzymes involved in estrogen formation--sulfatase and aromatase in breast fibroadenoma--contribute to the hypothesis that this disease may be hormone-dependent.

Adolescent↗
PubMed1983

Simultaneous azo-coupling method for an estrogen sulfatase in human tissues.

A simultaneous azo-coupling method for the histochemical localization of d-equilenin sulfatase is described. d-Equilenin is a natural estrogenic steroid hormone, and its sulfuric acid ester was synthesized. It was found that the d-equilenin liberated during hydrolysis of d-equilenin sulfate by tissue sulfatase could be coupled with a diazonium salt to produce a purple precipitate indicating enzyme activity. d-Equilenin sulfatase was found in human tissues, but not in tissues of the rat. The optimum substrate concentration was 0.8 mM, activity was demonstrable over the wide pH range 5.0-8.0. Enzyme activity localized diffusely in the cytoplasm in optimally fixed specimens. Enzyme activity was also fairly well demonstrable in unfixed cryostat sections. Enzyme activity was completely inhibited by 0.1 M phosphate, 1 mM sodium tetraborate, 1 mM p-nitrophenyl sulfate and by 2 mM p-nitrocatechol sulfate. Estrone sulfate at concentration 0.8 mM had no effect, but at 4 mM caused marked inhibition of the reaction. At the same concentrations dehydroepiandrosterone sulfate did not inhibit the reaction. The chemical properties and tissue localizations of d-equilenin sulfatase differed from the properties of arylsulfatases A, B and C and other steroid sulfatases reported previously in the literature.

17-Ketosteroids↗
PubMed1984

Detection of the Sanfilippo D syndrome by the use of a radiolabeled monosaccharide sulfate as the substrate for the estimation of N-acetylglucosamine-6-sulfate sulfatase.

N-Acetylglucosamine-6-sulfate sulfatase activity was assayed by incubation of the radiolabeled monosaccharide N-acetylglucosamine [1-14C]6-sulfate (GlcNAc6S) with homogenates of leukocytes and cultured skin fibroblasts and concentrates of urine derived from normal individuals, patients affected with N-acetylglucosamine-6-sulfate sulfatase deficiency (Sanfilippo D syndrome, mucopolysaccharidosis type IIID), and patients affected with other mucopolysaccharidoses. The assay clearly distinguished affected homozygotes from normal controls and other mucopolysaccharidosis types. The level of enzymatic activity toward GlcNAc6S was compared with that toward a sulfated disaccharide and a sulfated trisaccharide prepared from heparin. The disaccharide was desulfated at the same rate as the monosaccharide and the trisaccharide at 30 times that of the monosaccharide. Sulfatase activity toward glucose 6-sulfate and N-acetylmannosamine 6-sulfate was not detected. Sulfatase activity in fibroblast homogenates with GlcNAc6S exhibited a pH optimum at pH 6.5, an apparent Km of 330 mumol/liter, and inhibition by both sulfate and phosphate ions. The use of radiolabeled GlcNAc6S substrate for the assay of N-acetylglucosamine-6-sulfate sulfatase in leukocytes and skin fibroblasts for the routine enzymatic detection of the Sanfilippo D syndrome is recommended.

Cells, Cultured↗
PubMed1989

Sanfilippo D syndrome: estimation of N-acetylglucosamine-6-sulfatase activity with a radiolabeled monosulfated disaccharide substrate.

N-Acetylglucosamine-6-sulfatase activity was assayed by incubation of the radiolabeled disaccharide O-(a-N-acetylglucosamine-6-sulfate)-(1----3)-L-[6-3H]-idonic acid (GlcNAc6S-IdOA), with homogenates of leucocytes, cultured fibroblasts, and urine from normal individuals, patients affected with N-acetylglucosamine-6-sulfatase-deficiency (Sanfilippo D syndrome, mucopolysaccharidosis type IIID), and patients affected with other mucopolysaccharidoses and lysosomal storage disorders. The assay clearly distinguished affected homozygotes from their obligate heterozygotes and normal controls and other lysosomal storage disorders. Sulfatase activity in fibroblasts, leucocytes, and urine toward GlcNAc6S-IdOA exhibited a pH optimum at 4.2, 4.5, and 5.1, respectively. Sulfatase activity in fibroblasts had an apparent Km of 7.2 microM and was significantly inhibited by both sulfate and phosphate ions. The action of fibroblast or leucocyte N-acetylglucosamine-6-sulfatase activity toward GlcNAc6S-IdOA is recommended for the routine enzymatic detection and classification of mucopolysaccharidosis type IIID patients.

Amnion↗
PubMed1984

Estrone sulfatase activity in the human brain and estrone sulfate levels in the normal menstrual cycle.

When the plasma concentrations of estrone sulfate (E1S) were measured in five menstrual cycles, the highest concentrations were found on the day of LH peak (14.25 nmol/l +/- 2.94 [SE]). Peak levels of E1S were 20 times higher than the highest E2 levels measured (0.769 +/- 0.276 nmol/l). To determine whether E1S can be metabolized by adult and fetal tissues we examined estrone (E1) sulfatase activity in brain and other tissues. E1 Sulfatase activity was present in all tissues studied including adult endometrium, fat and skin. When the rate of sulfatase activity was measured in homogenates of fetal hypothalamus, frontal cortex and pituitary (n = 4), the hypothalamic activity (306.0 +/- 39.1 [SE] pmol/min/mg protein) was significantly higher than that of the frontal cortex (127.4 +/- 19.4, P less than 0.002) or pituitary (193.7 +/- 43.3, P less than 0.03). This was not apparent in the adult (n = 2) where the enzyme activity was similar in the hypothalamus (413.9 +/- 27.3) and frontal cortex (446.3 +/- 82.2) and lower in the pituitary (98.2 +/- 19.2). The Km for E1 sulfatase in the fetal frontal cortex was 28.9 microM. The high E1 sulfatase activity in estrogen responsive target tissues, particularly fetal hypothalamus, accompanied by a large circulating reservoir of E1S, suggest that this enzyme could possibly have a regulatory role in controlling the level of intracellular estrogens and in modulating their intracellular function.

Adult↗